Archive for February, 2008

Feb

28

2008
 
 

The woe of leks



Rare Gunnison sage-grouse populations sag because of their own mating behavior

Gunnison sage-grouse looks a bit like this...Pity the poor Gunnison sage-grouse Centrocercus minimus. Teetering on the edge of extinction, the recently described bird, found only in southwestern Colorado and southeastern Utah, suffers from the loss of almost three quarters of its brood, according to a two-year study published recently in Biological Conservation. Using a combination of painstaking field observation and computer simulation, University of Nebraska-Lincoln biologist Robert Gibson and colleagues also found that the sage-grouse is a victim of its own lek-based mating system: the handful of males that do almost all of the mating bring the effective population size dangerously low to the threshold needed to fend off the worst effects of inbreeding. Because only a few males mate, and only a few females’ chicks subsequently survive, it’s as though the population is much smaller than it really is. There’s rare, and then there’s rare. Source: Stiver JR, Apa AD, Remington TE & Gibson RM (2008) Polygyny and female breeding failure reduce effective population size in the lekking Gunnison sage-grouse. Biological Conservation DOI: 10.1016/j.biocon.2007.10.018

Image © Dave Menke

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Feb

22

2008
 
 

Catch ‘em while you can



Knowing the best time to trap elusive female mink saves wasted effort

Slippery when wetAugust and September are the best months in which to set traps for invasive American mink Mustela vison, according to a study published in the Journal of Nature Conservation. The imported carnivores devastate vulnerable waterbird breeding populations on small coastal islands and islets throughout Britain and continental Europe, yet trapping campaigns usually end up with a heavily male-biased harvest. Unfortunately, long-term reductions can only be achieved by removing females, but Clive Craik at the Scottish Association for Marine Science has found a way to maximize results: concentrate trapping effort when mink litters are becoming more mobile, and adult females are able to move around more. Female catch rates are almost eight times higher during those late summer months, so a big push at that time should be the best way to control the little blighters. Source: Craik JCA (2008) Sex ratio in catches of American mink — how to catch the females. Journal of Nature Conservation DOI: 10.1016/j.jnc.2008.01.003

Image © Frank Leung

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Feb

20

2008
 
 

Statistical glitch conjures fish



Reanalysis shows the Gulf of Mexico fishery didn’t collapse after all

In great big letters...Measuring stuff is difficult, as a paper published this week in PNAS makes clear. The widespread marine ecosystem collapse reported in the Gulf of Mexico was an artifact of the fisheries data that were collected and used, according to a reanalysis carried out by Louisiana State University marine biologist James Cowan and colleagues. Regional catches are dominated by the commercially important and targeted menhaden Brevoortia patronus and several penaeid shrimp species, but because they’re at the low end of the food chain they skew measures of ecosystem health based on fisheries landing data (the “mean trophic level index”, which provides a rough and ready indication of how overfished or degraded a marine community is). Using data from the National Marine Fishery Service, rather than the Food and Agriculture Organization, Cowan’s group found that only 21 percent of Gulf fisheries collapsed between 1950 and 2001 (and 8 percent have since recovered), whereas almost four-fifths would have been designated as collapsed under formerly used criteria. The key lies in incorporating management practices: even subtle changes in the way fleets operate can bring about significant differences in the composition of catches. Monitoring marine ecosystems is a complex task that we clearly haven’t mastered, but watch this space: the debate surely isn’t over. Source: de Mutsert K, Cowan JH Jr, Essington TE & Hilborn R (2008) Reanalysis of Gulf of Mexico fisheries data: landings can be misleading in assessments of fisheries and fisheries ecosystems. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0704354105

Image © Rob Stegmann

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Feb

15

2008
 
 

Poles apart, for now



Study paints grim picture of human impact on the world’s oceans

Map of destruction. The redder the color the worse the human impactA new marine “map” has allowed scientists to chart the human trail of destruction that currently blights some 41 percent of marine ecosystems. Writing in Science, a multidisciplinary group of authors, led by Ben Halpern at the National Center for Ecological Analysis and Synthesis, Santa Barbara gathered 17 global data sets covering a wide range of anthropogenic drivers, including invasive species, acidification, pollution, commercial shipping and fisheries bycatch rates. Many areas were affected by several factors together: the North Sea and Eastern Caribbean being particularly hard hit. We all know that coral reefs and mangroves are in trouble, but Halpern’s study shows that rocky reefs and continental shelves are suffering even more. Although the findings only provide an overview – the scale of the data misses finer detail – they clearly show how multiple pressures can accumulate. The least affected areas appear to be those tricky-to-reach polar regions, but with climate change expected to free up access to many currently ice-bound seas, who’s prepared to bet on that remaining the case? Source: Halpern BS, Walbridge S, Selkoe KA, Kappel CV, Micheli F, D’Agrosa C, Bruno JF, Casey KS, Ebert C, Fox HE, Fujita R, Heinemann D, Lenihan HS, Madin EMP, Perry MT, Selig ER, Spalding M, Steneck R & Watson R (2008) A global map of human impact on marine ecosystems. Science DOI: 10.1126/science.1149345

Image © Benjamin Halpern

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Feb

14

2008
 
 

Nobody loves us



Invertebrates are the big losers in the palm oil gold rush

Pedalling palm oil at what cost to biodiversity?Oil palm is a major global source of vegetable oil, yet little is being done to understand the ecological effects of turning over large swathes of tropical forest to the crop. According to a study published recently in PLoS ONE, less than one percent of research on oil palm has focused on biodiversity issues. That’s a problem, because there is a positive correlation between the relative area of land under oil palm cultivation and the number of IUCN-listed threatened species. Worse still, say Ed Turner and Cambridge University Museum of Zoology colleagues, biodiversity-related research tends to concentrate on large animals and birds, whereas it’s the insects that represent the majority of animal species, and which also have the biggest impact on ecosystem function. Addressing the knowledge gap of how oil palm agriculture affects invertebrates could bring important management insights, such as new forms of biological pest control. But for the moment, beetles, bugs and butterflies remain unloved and poorly understood. It’s always the little guys that suffer most. Source: Turner EC, Snaddon JL, Fayle TM & Foster WA (2008) Oil palm research in context: identifying the need for biodiversity assessment. PLoS ONE DOI: 10.1371/journal.pone.0001572

Image © Rick Olson

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Feb

12

2008
 
 

…and into the fire



Salmon farms destroy wild populations, global data reveal

It was this big, covered in lice, and three years ago...More evidence of the negative impact of salmon farms on wild populations is published today in PLoS Biology. Dalhousie University researchers the late Ransom Myers and former student Jennifer Ford, now at the Ecology Action Centre, Nova Scotia, studied catch rates of wild salmon living near fish farms off the Irish, Scottish and Canadian coasts. Populations “exposed” to fish farms – whereby migrating juveniles swimming past the holding pens are assaulted by parasites, disease and the unwelcome advances of amorous escapees – have plummeted across the board. In return for a farmed harvest of 1450 tonnes in 2003, for example, the wild Newfoundland population’s recruitment rate dropped by a staggering 63 percent. Decreases of 50 percent per generation are commonplace. The data build on an earlier, smaller scale study, and make fish farms look ever more unsustainable. It’s almost enough to make one long for the good old days of over-exploitation! Source: Ford JS & Myers RA (2008) A global assessment of salmon aquaculture impacts on wild salmonids. PLoS Biology DOI: 10.1371/journal.pbio.0060033

Related story in Conservation magazine: 10 Solutions to Save the Ocean | Salmon Farms Create Deadly Clouds of Sea Lice

Image © Bill Raboin

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Feb

5

2008
 
 

A pile of carp



Fish invasions around the world are linked to GDP, study finds

These hungry carp are in a moat, but others are invading rivers near youHuman activities are the best predictor of the extent to which a freshwater ecosystem has been invaded by non-native fish, according to a study published today in PLoS Biology. Fabien Leprieur and colleagues studied data on 9968 fish species from 1055 river basis around the world, their aim being to unravel the mysteries of what makes some areas more prone to non-native invasions than others. Gross domestic product — which serves as a useful proxy for how much we’ve degraded our environment (the relationship being positive, of course) — closely mirrors the pattern of fish invasions, with six global hotspots identified: the Pacific coast of North And Central America, southern South America, western and southern Europe, Central Eurasia, South Africa and Madagascar, and southern Australia and New Zealand. Leprieur’s findings are actually good news, because they hint at ways to predict which areas might be most vulnerable to invasions in the future. As the CNRS-Université Paul Sabatier, Toulouse, researcher points out, developing countries with booming economies are the most likely to suffer the same ecological fate as the old empires. At least we can plan for it this time. Source: Leprieur F, Beauchard O, Blanchet S, Oberdorff T & Brosse S (2008) Fish invasions in the world’s river systems: when natural processes are blurred by human activities. PLoS Biology DOI: 10.1371/journal.pbio.0060028

Related story in Conservation magazine: Snakes On Planes

Image © Nick Atkinson

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